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• TAPA-TFPB-COFs was simply synthesized at room temperature. • TAPA-TFPB-COFs were explored as sorbents for the SPE of PCAs. • The established SPE-HPLC-MS/MS method was sensitive and accurate. • This method satisfied the analyzation of PCAs in environmental water samples. The determination of traces levels of pesticide residue in water is crucial for monitoring water quality. In this study, covalent organic frameworks (COFs), namely TAPA-TFPB-COFs were prepared at room temperature (25 °C) and applied as adsorbents for the solid phase extraction (SPE) of phenoxy carboxylic acid herbicides (PCAs). The extraction was followed by analyzation using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Under the optimal conditions, ultrasensitive and specific analysis of PCAs in water samples was achieved. The method exhibited high sensitivity with low limits of detection (0.08–0.28 ng L−1), good linearity in the range of 1.00 to 200 ng L−1 and satisfactory repeatability (intra-day: 3.72–5.30%; inter-day: 2.02–4.04%). The method was successfully applied to the analyzation of trace PCAs in tap, well, and river water and the spiked recoveries were in the range of 81.1–112%. These results indicate that the SPE-LC-MS/MS technique with TAPA-TFPB-COFs as the SPE adsorbent is a promising technique for the detection of trace levels of PCAs in environmental water samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • K, P, O and S were innovatively simultaneously doped into g-C 3 N 4. • K, P, O, S-g-C 3 N 4 has 12.85 times higher yield of H 2 O 2 than g-C 3 N 4. • The degradation rate of TC by K, P, O, S-g-C 3 N 4 was 1.5 times higher than the pure. • Four elements doping can promote the charge transfer in g-C 3 N 4. • Negatively charged S introduced into the g-C 3 N 4 can facilitate the ·O 2 − production. Elemental doping can modulate the electronic and molecular structure of g-C 3 N 4 to improve its photocatalytic properties. In this study, potassium (K), phosphorus (P), oxygen (O), and sulfur (S) were doped into the g-C 3 N 4 photocatalyst (K, P, O, S/g-C 3 N 4), and the four-element doped photocatalyst was successfully prepared. UV–vis diffuse reflection spectroscopy, photoluminescence, and transient photocurrent revealed that the co-doping of g-C 3 N 4 with K, P, O and S broadens the visible response and accelerates the transfer of photogenerated charges. Under visible light irradiation, the H 2 O 2 concentration produced with K, P, O, S/g-C 3 N 4 was 12.85 times higher than that with g-C 3 N 4. Moreover, tetracycline (TC) can be effectively degraded by the photocatalyst in surface water. The degradation pathway of TC and the molecular structures of 12 intermediates were analyzed by liquid chromatography-mass spectrometry. The superoxide radical (·O 2 −) trapping-electron spin resonance (ESR) technique confirmed that ·O 2 − is the main active species in the system. Therefore, the four-element doping strategy adopted in this research proved the feasibility of increasing the amount of H 2 O 2 produced and degrading the antibiotics in natural water under visible light. [ABSTRACT FROM AUTHOR]

• A novel magnetic covalent organic framework (NH 2 –Fe 3 O 4 @COF) was synthesized and used as a MSPE adsorbent. • Adsorption mechanism of benzoylurea insecticides (BUs) on NH 2 –Fe 3 O 4 @COF was elucidated by DFT study. • Low limits of detection, good precision, and wide linearities were obtained by the proposed MSPE–LC–MS/MS method. A novel magnetic covalent organic framework (NH 2 –Fe 3 O 4 @COF) was prepared using a simple room-temperature synthesis in this study. These magnetic particles exhibited high adsorption performance with short adsorption time (10 min) for six benzoylurea insecticides (BUs) as magnetic solid-phase extraction (MSPE) adsorbents. Quantum chemistry calculation demonstrated that adsorption mechanism was primarily attributed to strong halogen bonds between electronegative O atoms of COF and electropositive F atoms of BUs as well as potential hydrophobic effect. Wide linearities (10–1000 ng·L−1) and low limits of detection (0.06–1.65 ng·L−1) for six analytes were obtained via liquid chromatography–tandem mass spectrometry. Applicability of the proposed method was further evaluated by analyzing four kinds of original tea beverages. Recoveries of six BUs in spiked samples ranged from 80.1% to 108.4%. [ABSTRACT FROM AUTHOR]